Using the APIs of Facebook and Foursquare, WKWYD mines the public status updates and check-ins of random strangers and republishes them, telling us who’s unhappy at work, been partying a bit too hard, or is a little too generous with their contact information.

This “experiment” is the product of 18-year-old British Web developer Callum Haywood, who is now just a bit more famous than he was 24 hours ago. According to Haywood’s Twitter feed, more than 100,000 people have visited WKWYD in its first 27 hours of existence – most likely thanks to a brief writeup by TheNextWeb’s Drew Olanoff. When I visited, the site displayed a message saying it’s struggling to keep up with all the traffic it’s getting.

WKWYD is kind of the bastard offspring of Openbook.com (where you can search public Facebook status updates in real time) and Please Rob Me (which gathered public check-ins from Foursquare and its ilk, alerting strangers when you’d be away from home – or did, until its creators felt their point had been made and retired it). The key difference is that Haywood is a bit more careful to avoid revealing too many details about the subjects of his experiment.

Users are listed by first name and last initial only, and unlike Openbook or Please Rob Me, you can’t immediately jump to the profile of the person who stupidly just called his boss a term normally associated with basic bodily functions, or call up the home address of the person who just left for a three week camping trip.

And that’s a good thing. Take this post from Anastasia R., for example:

I’m getting so mad right now I hate my boss Jay I hope he dies better yet I feel like killin him if you in a bad mood don't take it out on everyone at the job like wtf its way to hot to take your s***

Now imagine you’re Anastasia’s boss. Or, I should say, her ex boss – because what person in their right mind would keep her on after reading that update? (Not to mention Anastasia’s apparent illiteracy.)

WKWYD lets you mine Foursquare public check-ins, displaying Google Street View photos of various locations by longitude and latitude (but no street addresses). You can also install a Facebook app that reveals all the places you’ve checked into – or been checked in by other people – but the app reveals that information only to you.

The lesson here? The same one you’ve been hearing for a while now: You should think about maybe considering being a tad more circumspect with what you post online. As Facebook data becomes something that seemingly every company wants to mine and monetize, that message is more relevant than ever.

Got a question about social media? TY4NS blogger Dan Tynan may have the answer (and if not, he’ll make something up). Visit his snarky, occasionally NSFW blog eSarcasm or follow him on Twitter: @tynanwrites. For the latest IT news, analysis and how-to’s, follow ITworld on Twitter and Facebook.